(a) Field of the Invention
The present invention relates to a portable data-processing device, and more particularly, to a multi-function portable data-processing device allowing an improved key input operation.
(b) Description of the Related Art
It is desired that portable data-processing devices, such as a cellular phone or personal digital assistant, have lighter weight as well as multiple functions. For example, the cellular phone generally has functions of telephone directory, receiving/transmitting e-mails and internet accessing besides the ordinary telephone function. For achieving the ordinary telephone function, it is generally sufficient that the cellular phone have a numerical keyboard. On the other hand, for achieving the telephone directory function or e-mail receiving/transmitting function, letter keyboards should be provided for inputting letters such as alphabetic characters or other characters. For a practical view point, however, it is generally impossible for the cellular phone having a limited scale to mount thereon such a letter keyboard besides the numerical keyboard. Thus, the cellular phone generally includes at most a numerical keyboard including numerical keypads for typing numerical characters including zero to nine, # keypad, * keypad, and some limited functional keypads on the operational panel which is disposed separately from a liquid crystal display (LCD) unit. Each of letters or symbols is allocated to one of these keypads, which enters different characters or symbols after iterative depression thereof to thereby reduce the number of keypads on the cellular phone.
Some portable data-processing device on the market has a touch-sensitive panel provided on the LCD unit, which generally represents thereon typed letters, telephone number or the contents of the e-mail. The touch-sensitive panel has a specific transparent film which is either a conductive film or a resistor film having a plurality of labeled portions to be depressed or touched, to allow execution of a specified function allocated to each labeled portion.
It should be noted however that, if the LCD unit provided as a single display unit on the cellular phone has a touch-sensitive panel function thereon, there arises an inconvenience that the ordinary representation on the screen of the LCD unit is difficult to observe. In addition, when the touch-sensitive panel is to be used as an input device on the screen of the LCD unit, all or some part of the screen of the LCD unit represents images for the touch-sensitive panel to nullify or limit the area for the ordinary representation on the screen. It may be considered to provide a dedicated LCD unit for the touch-sensitive panel function on the cellular phone in addition to a main LCD unit. In such a case, the main LCD unit can represent an ordinary image on the screen thereof even in the case where a plurality of functions are allocated to a single keypad or a full-keyboard is provided on the touch-sensitive panel. This increases the dimensions of the cellular phone however, and thus is difficult to employ.